Catalytic polymerization of unsaturated esters



' ization of allyl esters Patented June 18, 1946 UNITED STATE CATALYTIC POLYMERIZATION F UNSATURATED ESTERS David E. Adelson, Berkeley, Calif., Robert P. Ruh, Columbus, Ohio,-- and Harold F. Gray, Jr., Berkeley, Calif., assignors to Shell Develop:- ment Company, San'Franclsco, Caliifl, a-corpo-' ration of Delaware No Drawing. Application June -14, 1943, Serial No. 490,952

15 Claims. 1

This invention relates to a process for the cat-v alytic polymerization of unsaturated esters. More particularly, the invention pertains to polymernd related compounds, the polymerization being effected catalytically by the presence of a new class of polymerization catalysts consisting of certain metal salts,

Unsaturated esters of the type of allyl acetate obtainable fr'om a monocarboxylic acid which is devoid of any polymerizable unsaturated group and an unsaturated alcohol having an olefinic linkage between two carbon atoms one of which is directly linked to a saturated carbon atomhaving a hydroxyl group linked directly thereto, are compounds which may be termed diiiicultly polymerizable substances. While the action of heat, light or-peroxldlc substances has been-used to obtain polymers from unsaturated esters-oi this type, none effects a rapid olymerization of the compounds and each of such catalysts is accompanied with certain disadvantages which areovercome by the present invention.

It is an object of the present invention to provide a method of polymerizing allyl acetate and related compounds. l v

. Another obiect is to provide a process for obtaining polymers oi unsaturated esters of the type of allyl acetate-employing as catalytic agent,

therefor a class oi metal salts.

A further object is to provide a class of" new polymerization catalysts.

These and other objects will be apparent from the description of the invention s'iven hereinafter.

we have now discovered that allyi acetate and related compounds are catalytically polymerized when heated in the presence of a cadmium or mercuric salt of a carboxylic acirt. These compounds employed as catalyst are arboxyiic acid salts of a bivalent metal of the group consisting of cadmium and mercury. Any carboxylic acid salt of these metals, wherein thecadmium or mercury is in a bivalent state of valency, is suitable as catalyst in the process of the invention.

Representative salts include cadmium or mercuric tor-mate. acetate, .propionate, butyrate, chloracetate, .isobutyrate, ,phthalate. 'malonate, succinate, maleate. valerate, palmitate,- stearate,

bromstearate, tartrate, malaise-etc. These compounds are cadmium or mercuric salts or carboxylic acids containing no other elements than carbon, hydrogen, oxygen and halogen.

Preferably. salts of saturated fmonocarboxylic, acids containing not more than 6,carbon atoms are employed. Cadmium acetate and mercuric acetate arethe most preierredsalts. The cat- Cadmium Mercuric H Hours Blank acetate acetate Average rate oi increase in units perhr... 0.108 0.370 0.180

alytic eiiect of these salts is evident from the results tabulated below which wereobtained in polymerizing allyl acetate, a difficultly polymerizable ester, in their-presence. The monomeric allyl acetate was substantially pure and anhydrous and to separate quantities was added 0.5% anhydrous cadmium acetate or mercuric acetate.

The esters were refluxed or boiled at normal pressure in the presence of the salts in a vessel fitted with a reflux condenser and the course of the polymerization was followed by observation of the refractive index of the reaction mass taken from time to time after starting the'heating. The refractive index of the polymer which was polyallyl acetate was considerably higher than.

.' that of the monomer so that an increase of refractive index indicated that polymerization was occurring; A blank to which no salt was added was similarly heated for comparison and the rezosults of this experiment are also listed below.

The valuesgiven in the body of the table are the increase in fourth decimal place units of the refractive index (An/Dx10 for the indicated time from start.

The increase in refractive index is approximately proportional to the rateoi polymer formation at. the substantially uniform temperature employed and the results tabulated above indif cate that while the heating of the allyl acetate in the absence of a catalyst slowly effects the polymerization of the ester, the rate of polymer formation is improved by the presence of the catalytically active salts.

The compounds polymerized according to the process oi the invention are unsaturated esters of of which contains at least one hydrogen atom linked directly thereto and one of which is linked directly to a saturated carbon atom containin the hydroxyl group linked directly thereto. Preferably the ester is derived from a mono-unsaturated alcohol containing a vinylidene group directly linked to a saturated carbon atom to which is linked the hydroxyl group. Unsaturated esters of aromatic acids such as benzoic acid, toluic acid, and the like are included within the perview of the invention since the lack of saturation of the carbon atoms in the aromatic ring of such compounds is responsible for no polymerizable unsaturated groups therein because of the wellknown peculiarities of aromatic nuclei. The esters of saturated monocarboxylic acids constitute a preferred group and while esters of simple saturated acids are particularly preferred, also included are those esters of saturated aliphatic acids wherein one or more hydrogen atomshave been substituted by a halogen atom, a hydroxyl group, an alkgxy group, and aryl oxy group and like groups. Among the preferred reactants are included such compounds as allyl formate, allyl acetate, allyl propionate, allyl isobutyrate, betamethylallyl acetate, beta-chlorallyl acetate, betaethylailyl formate, beta-phenylallyl acetate, betamethoxyallyl acetate, beta chloromethylallyl acetate, allyl benzoate, beta-methylallyl propionate,

allyl toluate, allyl salicylate, allyl glycolate, allyl methoxyacetate, beta-methylallyl chloracetate, 4o

allyl butryrate, aipha-methylallyl acetate, alpha- 5 phenylaliyl acetate, allyl ethoxyformate, betamethylallyl phenoxyformate, allyl naphthoate, allyl ester of hydrogenated abietic acid, and the like.

The preferred compounds of the group may be represented by the general formula,

4 higher esters requires the use of an inert solvent in order to have the reaction mixture liquid in effecting the polymerization. For this purpose solvents such as saturated esters like ethyl acetate, isopropyl acetate, butyl acetate, etc.; hydrocarbons like benzene, toluene hexane, octanes, tc.; ethers like dioxane, dibutyl ether, beta-dichlorodiethyl ether etc., are admixed with the unsaturated ester subjected to polymerization. In. general, however, it is preferred to avoid the use of solvents or diluents where possible since they complicate the recovery problem in obtaining the polymer and decrease the rate of the polymerization reactions. It is preferred to employ as reactant an unsaturated ester which is liquid under the reaction conditions as is realized with lower esters or esters of lower unsaturated alcohols. These preferred reactants contain not more than seven carbon atoms in the unsaturated ester.

While the salts employed as catalyst dissolve to a greater or lesser extent in the reaction material, they are normally soluble in only minute amounts so that the reaction mixture is contacted with the catalyst as a crystalline substance. For this reason its is preferable to utilize the salt in the finely divided or comminuted state. Amounts of catalyst from a few hundredths of 1% to 5% or more per cent are effective in catalyzing the reactions.

The cadmium or mercuric salts of the carboxylic acids which are employed as catalyst in polymerizing the unsaturated estershave advantages not realized with known catalyst such as benzoyl peroxide, one of the most commonly used materials for this purpose. Since they are essentially insoluble in thereaction mixture, the polymer obtained is not contaminated with materials such as benzoic' acids and other decomposition produets obtained when benzoyl peroxide is utilized. Further, upon completion of the polymerization operation, the catalyst is filtered from the reaction mixture and can be used again.

In extending the process of the invention the unsaturated ester to which had been added an amount of catalyst is heated between 50 and 150 C. and the heating continued until the desired meric material. After 25 to 35% or more of the reactant has been converted to polymer, as may be determined by observation of increase of the refractive index, the heating is discontinued and 1 the reaction material filtered to remove catalyst.

wherein R1, R2 and R: represent hydrogen atoms, halogen atoms or hydrocarbon radicals and R4 represents a hydrogen atom or an organic radical devoid of a polymerizable unsaturated group,

such as an alkylgroup, an a yl group, an alicyclic 0 group, an aralkyl group, an alkoxy group, an aryl oxy group, and the like.

Less preferred esters include compounds like crotyl acetate, crotyl propionate, crotyl benzoate,

2-hexenyl acetate, Z-pentenyl formate, 2-isopentenyl chloracetate, methyl .isobutenyl carbinyl butyrate, and similar types of esters.

The polymerization is effected by heating the unsaturated ester under anhydrous conditions in the presence-of or in contact with the catalyst 7 salts at a temperature of 50 to 150 C. with the ester in the liquid phase. With unsaturated esters of sumciently low melting point so that they are liquid under the reaction condition, the ester zation reaction when the catalysts of the present invention are employed. In some cases it is desirable to intermittently add fresh catalyst to the reactionmaterial during the course of the heating rather than adding the entire amount at the start.

Another method of effecting the reaction which is adapted for continuous production of polymer is polymerized in the proces per se, The use of realized with the catalyst salts is to pass the liquid reactant material through a bed of the salt. In adapting this procedure to continuous operation the organic material is circulated through a bed of the catalyst maintained at the desired temperature and monomeric ester'is fed into the cycling system while material is withdrawn therefrom, the withdrawn portion being a mixture of polymer and monomer from which the monomer is recovered for return to the cycling system.

The polymers prepared according to the invention have application as plasticizers and softeners for various materials. Further, the solubility in various substances makes the polymeric esters useful intermediates in the synthesis of polymeric alcohols which may be prepared byhydrolysis or saponification of the polymers.

For the purpose or iurther'illustrating the invention the following specific example is given, but.

it is to be understood thatthe invention is not to be construued as limited to any details given therein.

' Example distilled at 100 C. under 1 mm. pressure in a cur rent of carbon dioxide gas in order to recover I the unreacted monomer. The distillate consisted of about 64.5 grams of allyl acetate having a re- 6' .boxylic acid salt or a bivalent metal from the group consisting of cadmium and mercury, said saturated carboxylic acid containing no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time sufllcient to effect appreciable said ester.

4. A process for the production of a polymer of a mono-oieflnic ester of a monocarboxylic acid and a monohydric alcohol having a vinylidene group directly linked to a saturated carbon atom containing the hydroxyl group linked directly thereto, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a tempera- C. in the presence of a neutral saturated carboxylic acid salt of a bivalent metal. from the group consisting or cadmium and mercury, said saturated carboxylic acid containing no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time sufliclent to. effect apfractive index of An20/D=l.4040 or a recovery of about 72.1%. The polymeric residue amounted to about 24.8 grams indicating a conversion of 27.7% had been realized. The polyailyl acetate was a yellow viscous mass which analyzed as follows:

We claim as our invention:

1. A process for the' production of poiyallyl acetate which consists of boiling allyl acetate at atmospheric pressure under anhydrous and non-oxidizing conditions in the presence of cadmium acetate .for a time sufllcient to effect appreciable polymerization of the allyl acetate.

'2. A process for the production of polyallyl acetate which consists of boiling allyl acetate at atmospheric pressure under anhydrous and nonoxidizing conditions in the presence of mercuric acetate for a time sumcient to eflect appreciable polymerization of the allyl acetate.

3. A process for the production or a polymer of a mono-olefinic ester or a monocarboxylic acid and a monohydric alcohol having an oleflnic linkage between two carbon atoms one of which contains at least one hydrogen atom linked directly thereto and the other of which is linked directly to a saturated carbon atom having the hydroxyl group linked directly thereto, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of a neutral saturated carpreciable polymerization of said ester.

5. A process for'the production of a polymer of an allyl ester or a saturated monocarboxylic acid, which ester contains not more than '1 carbon atoms, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperatureof C. to 150 C. in the presence of a neutral saturated carboxylic acid salt of a bivalent metal from the group consisting of cadmium and mercury, said saturated carboxylic acid containing no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time a neutral cadmium salt of ,acid containing not more suflicient to effect appreciable polymerization of said ester.

6. A process for the production or a polymer of amono-olefinic ester of a monocarboxylic acid and a monohydric alcohol having an olefinic linkage between two carbon atoms one of which contains at least one hydrogen atom linked directly thereto and the other of which is linked directly to a saturated carbon atom having the hydroxyl group linkeddirectly thereto, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of a neutral cadmium salt of a saturated carboxylic acid containing not more than 6 carbon atoms and no other elements than carbon, hydrogen. oxygen and halogen, and said heating being continued for a time sufiicient to effect appreciable polymerization of said ester.

7. A process for the production of a polymer of a mono-oleiinic ester of a monocarboxylic acid and a monohydric group directly linked to a saturated carbon atom containing the hydroxyl group linked directly thereto, which ester contains only double-bonded unsaturation and no other elements than carbon. hydrogen, oxygen and halogen. which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of and no other elements-than carbon, hydrogen, oxygen and halogen, and said heating being continued tor a time suiflcient to effect appreciable polymerization of said ester.

polymerization of alcohol having a vinylidene a saturated carboxylic than 6 carbon atoms- 8. A process for the production of a polymer of an allyl ester of a saturated monocarboxylic acid, which ester contains not more than 7 carbon atoms, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of a neutral cadmium salt of a saturated carboxylic acid containing not more than 6 carbon atoms and no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time sufificient to effect appreciable polymerization of said ester.

9. A process for the production of polyallyl acetate which consists of heating allyl acetate under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of a neutral cadmium salt of a saturated carboxyllc acid containing not more than 6 carbon atoms and no other elements than carbon, I

hydrogen, oxygen and halogen, and said heating being continued for.a time suflficient to effect appreciable polymerization of the allyl acetate.

10. A process for the production of polymer which consists of heating in liquid phase a monoolefinic ester of a saturated monocarboxylic acid and a monohydric alcohol having a vinylidene group directly linked to a saturated carbon atom containing the hydroxyl group linked directly thereto, which ester contains only double-bonded unsaturation and no other elements than car bon, hydrogen, oxygen and halogen. said heating being effected under anhydrous and non-oxidizing conditions at a temperature of 50 to 150 C. with the ester in the presence of cadmium acetate for a time suiilcient to efl'ect appreciable polymerization of said ester.

11. A process for the production of polymer which consists of heating in liquid phase a monoolefinic ester of a saturated monocarboxylic acid and a monohydric alcohol having a vinylidene group directly linked to a saturated carbon atom containing the hydroxyl group linked directly thereto, which ester. contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and halogen, said heating being effected under anhydrous and non-oxidizing directly to a saturated carbon atom having the hydroxyl group linked directly thereto, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen. oxygen and halogen, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of a neutral mercuric salt of a saturated carboxylic acid containing not more than six carbon atoms and no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time suflicient to effect appreciable polymerization of said ester.

13. A process for the production of a polymer of ,a mono-olefinic monocarboxylic acid and a monohydric alcohol having a vinylidene group directly linked to a saturated carbon atom containing the hydroxyl group linked directly there to, which ester contains only double-bonded unsaturation and no other elements than carbon, hydrogen, oxygen and hydrogen, which consists of heating said ester in liquid phase under anhydrous and non-oxidizing conditions at a temperature of 50 C.' to 150 C. in the presence of a neutral mercuric salt of a saturated carboxylic acid'containing not more than six carbon atoms and no other elements than carbon, hydrogen,

' ester of a saturated monocarboxylic acid, which ester contains not more than seven carbon atoms, which consists oi heating said ester in liquid phase under anhydrous and non-oxidizing condi- I tions at a temperature of 50 C. to 150 C. in the presence of a neutral mercuric salt of a saturated conditions at a temperature of to C. with the ester in the presence of mercuric acetate for a time sufficient to effect appreciable polymerization of said ester.

12. A process for the production of a polymer of a mono-olefinic ester of a monocarboxylic acid and a monohydric alcohol having an oleflnic linkage between two 'carbon atoms one of which contains at least one hydrogen atom linked directly thereto and the other of which is linked carboxylic acid containing not more than six carbon atoms and no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time sufllcient to eifect appreciable polymerization of said ester. 15. A process for the production of polyallyl acetate which consists of heating allyl acetate under anhydrous and non-oxidizing conditions at a temperature of 50 C. to 150 C. in the presence of a neutral mercuric salt of a saturated carboxylic acid containing not more than six carbon atoms and no other elements than carbon, hydrogen, oxygen and halogen, and said heating being continued for a time suflicient to effect appreciable polymerization of the allyl acetate.

' DAVID E. ADELSON.

HAROLD F. GRAY, J a.

ROBERT P. RUH. 

